The present invention relates to an apparatus for detecting the acupuncture points of a patient and for applying stimulating electrical signals to the detected points, of the type comprising a probe having a contact needle which is electrically connected to a generator of electric sawtooth signals, the rise time of each sawtooth being determined by a first capacitor and by a resistive circuit comprising, connected in series in use, a first fixed resistor, a variable resistor, said contact needle, the skin of the patient and an electrode held by the patient, and mode-changing means for selecting between an acupuncture point detection mode and an electrical stimulation mode, said mode-changing means comprising a first switch means connected to the resistive circuit for modifying the ohmic value thereof from a high ohmic value for the acupuncture point detection mode to a lower ohmic value for the electrical stimulation mode.
FIG. 1 of the enclosed drawings shows the simplified diagram of a known apparatus of the above-mentioned type. The sawtooth signal generator may be a conventional relaxation oscillator OSC formed for example by a unijunction transistor T, two resistors R.sub.1 and R.sub.2 and a capacitor C.sub.0. The emitter of the unijunction transistor T is connected through a fixed resistor R.sub.3 (which can be short-circuited by a switch I for the stimulation mode) and by a variable resistor P to the contact needle or stylus PT of a probe S. The emitter of the unijunction transistor T is also connected to a power amplifier, itself connected to a loudspeaker and/or an indicator or a device for displaying the sawtooth signals or their frequency (not shown in FIG. 1). In FIG. 1, E designates an electrode or a handle intended to be held by the patient, and R.sub.4 designates the resistance of the skin of the patient between contact needle PT and electrode E. The value of resistance R.sub.4 varies significantly according as the contact needle PT is placed on an acupuncture point or on the surrounding skin. By way of indication, R.sub.4 may have a value of 60 k.OMEGA. on an acupuncture point and 500 k.OMEGA. on the surrounding skin. These values themselves vary with individuals, the type of skin, the position of the acupuncture point, etc. FIG. 2 of the accompanying drawings shows the wave form of the sawtooth signals delivered by such an apparatus. The rise time t.sub.1 of each sawtooth pulse or charging time of capacitor C.sub.0 depends on the products R.C.sub.0, R being the sum of the ohmic values of resistor R.sub.3, variable resistor P and resistance R.sub.4. In practical operation, this time t.sub.1 also corresponds to the repolarization of the cutaneous point, this repolarization itself being required for efficient stimulation. t.sub.2 is the discharge time of capacitor C.sub.0 through the unijunction transistor T and resistor R.sub.2 to ground. This time t.sub.2 also corresponds to the depolarization or stimulation of the acupuncture point. The energy which is transferred is proportional to the value of the product .DELTA.V.t.sub.2 (hatched area in FIG. 2), .DELTA.V being the peak-to-peak voltage of the sawtooth signal (about 60% of the DC supply voltage V.sub.0).
For the detection mode (localization of the acupuncture point), the charging current of capacitor C.sub.0 as well as the discharge energy must be as small as possible, for example about 1 .mu.A, thus explaining the presence of resistor R.sub.3 (switch I being open) and of variable resistor P the value of which is adjusted according to the individual. On the other hand, for the stimulation mode (treatment of the acupuncture point) the energy to be supplied must be much higher, for example the current must be of the order of 50 to 160 .mu.A, which explains the presence of switch I for short-circuiting resistor R.sub.3.
Furthermore, to obtain good selectivity in the detection mode, i.e. for localizing with certainty the acupuncture point, the frequency (1/T.sub.0, with T.sub.0 =t.sub.1 +t.sub.2) of the sawtooth signal must be able to vary substantially according as the contact needle PT is placed on the acupuncture point or on the surrounding skin.
It results therefrom that the operation of the known apparatus as a detector and as a stimulator of acupuncture points is based on a compromise between the value of the capacity of capacitor C.sub.0 compatible with the two modes of operation and the ohmic value of resistor R.sub.3 whose short-circuiting by switch I must reduce, in the stimulation mode, the overall resistance of the resistive circuit (R.sub.3, P, R.sub.4) so as to increase the value of the current, the frequency of the sawtooth signal and, consequently, the number of energy transfers on discharge of capacitor C.sub.0. The compromise must also take into account the fact that in the two modes of operation, time t.sub.1 must be sufficient to allow the cutaneous tissue to be repolarized before the next discharge of capacitor C.sub.0. Accordingly, as in any compromise solution, it is not possible to obtain perfect operation both in the detection mode and in the stimulation mode.
Other apparatus are also known for detecting and stimulating acupuncture points which, so as to get free of the above problems, use a circuit in accordance with the diagram of FIG. 1 (without switch I) for the detection mode and another totally separate circuit capable of generating pulses of various types having different shapes and of a controlled frequency for the stimulation mode, either of these two circuits being able to be selectively connected of the contact needle by means of a mode selector. The known apparatus of this latter type do not take into consideration, or very little, the physiological problems inherent in electric stimulation, particularly problems of electric and progressive repolarization of the skin in accordance with natural laws and, accordingly, their efficiency is reduced thereby.